The present disclosure relates to a composite perovskite powder, a preparation method thereof, and a paste composition for an internal electrode having the same, and more particularly, to an ultra-fine composite perovskite powder used in a multilayer ceramic capacitor (MLCC), or the like, a preparation method thereof, and a paste composition for an internal electrode.
A barium titanate-based perovskite powder, or the like, a ferroelectric ceramic material, is used as a dielectric material in an electronic component such as a multilayer ceramic capacitor (MLCC), a ceramic filter, a piezoelectric element, a ferroelectric memory (FeRAM), a thermistor, a varistor, or the like.
In accordance with the current trend toward slimness and lightness, high capacitance, high reliability, and the like, in the area of electronic components, atomization of a barium titanate-based perovskite powder used as the ferroelectric material in multilayer ceramic capacitors (MLCC) has been required.
As preparation methods of such a barium titanate-based perovskite powder, there are provided a solid state reaction method and a wet method, but in the case of the solid state reaction method, since a crystalline phase is formed by high temperature calcination, there are disadvantages in that a high temperature calcination process and a grinding process are required, a shape of the synthesized particle may not be optimal, and particle size distribution may be relatively wide. In addition, it may be difficult to disperse the particles, due to lumping caused by heat treatment, and generally, a minimal particle size is significantly large (about 1 μm).
In the case of hydrothermally synthesizing the barium titanate-based perovskite powder using the wet method without heat treatment, the dispersion problem may be solved, and in hydrothermal synthesis, it is easy to control the shape of particles, in addition to particles having a small size and narrow particle size distribution being able to be synthesized.
Meanwhile, a dielectric layer and an internal electrode layer are present in the multilayer ceramic capacitor (MLCC), but there may be a problem, in that since an internal electrode may be sintered faster than the dielectric layer, as the MLCC is reduced in thickness, connectivity of the internal electrode may be further deteriorated. In order to solve this problem, at the time of preparing a paste for an internal electrode, a dielectric powder is mixed and used. Powder used for this purpose is referred to as an inhibitor.
The dielectric inhibitor powder in the paste for an internal electrode initially delays the sintering of the internal electrode and is discharged into the dielectric layer when the sintering of the internal electrode is completed. Since the inhibitor is formed of the same component as that of the dielectric layer, the inhibitor discharged into the dielectric layer may serve as a dielectric material after sintering.
However, although the inhibitor powder for an internal electrode is added, since there is still a significant difference in a sintering rate between the internal electrode and the dielectric layer, in the case in which the MLCC is thick, there is no problem, but as the MLCC is reduced in thickness, the connectivity of the internal electrode may be deteriorated.
In addition, as the MLCC is reduced in thickness, the inhibitor powder for an internal electrode should be further atomized, but in the case of ultra-fine particles, there are problems in that ions of barium, or the like, may be eluted into an aqueous system due to a large specific surface area, a composition ratio may be deviated, and aggregation of the particles may be severe.
A process of hydrothermally synthesizing fine barium titanate without heat treatment has been disclosed in the following Patent Document 1, but there is a limitation in preparing ultra-fine particles required for the inhibitor powder for an internal electrode of a miniaturized and thin multilayer ceramic capacitor (MLCC), and ions may be eluted into an aqueous system at the time of synthesis.